Drainage units or devices for collecting fluids, preferably liquids and perhaps entrained solids carried therewith from body cavities, are known in the art. Initially, such devices comprised a plurality of bottles connected by hoses. One such bottle would form the collection chamber for matter being drawn from a body cavity. Another bottle formed a water seal, through which gases from the collection chamber would be bubbled, and to which the vacuum was connected. A third bottle was generally constructed as a manometer for controlling the amount of vacuum, or negative pressure of the system, to a given pressure determined by water height.
Such systems gradually developed whereby the various bottles or containers comprising the system were built into a single unit, for ease of handling in hospitals, avoidance of bottle upset, and better efficiency in general.
The present state of the art of such drainage devices remains imperfect in that they are often characterized by undesirable transfer of liquid from one of the chambers, cavities, or receptacles to another, after upset. Other disadvantages reside in susceptibility to blockage of the air inlet, ready upsetting of the devices, difficulties of filling the devices with water leading to undesirable overfill or underfill, difficulty of use by ambulatory patients, inefficient construction requiring so much room that they are readily upset, and difficulties of observation by medical personnel for determining the functioning of the vacuum, the amount of liquid being accumulated, and many other parameters.